U.S. patent application number 13/934921 was filed with the patent office on 2014-04-10 for organic light emitting diode display and method for manufacturing organic light emitting diode display.
The applicant listed for this patent is Samsung Display Co., Ltd.. Invention is credited to Ki-Yeol Byun.
Application Number | 20140097415 13/934921 |
Document ID | / |
Family ID | 50432038 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140097415 |
Kind Code |
A1 |
Byun; Ki-Yeol |
April 10, 2014 |
ORGANIC LIGHT EMITTING DIODE DISPLAY AND METHOD FOR MANUFACTURING
ORGANIC LIGHT EMITTING DIODE DISPLAY
Abstract
An organic light emitting diode (OLED) display is disclosed. In
one aspect, the display includes a substrate, an organic light
emitting element positioned on the substrate, and a first thin film
transistor (TFT) connected to the organic light emitting element
and having a driving channel region including at least one
groove.
Inventors: |
Byun; Ki-Yeol; (Yongin-City,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Display Co., Ltd. |
Yongin-City |
|
KR |
|
|
Family ID: |
50432038 |
Appl. No.: |
13/934921 |
Filed: |
July 3, 2013 |
Current U.S.
Class: |
257/40 ; 257/88;
438/34 |
Current CPC
Class: |
H01L 27/3262 20130101;
Y02B 20/30 20130101; H01L 51/56 20130101; Y02B 20/36 20130101; H01L
51/5203 20130101; H05B 45/60 20200101 |
Class at
Publication: |
257/40 ; 257/88;
438/34 |
International
Class: |
H01L 51/52 20060101
H01L051/52; H01L 51/56 20060101 H01L051/56 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2012 |
KR |
10-2012-0112470 |
Claims
1. A organic light emitting diode (OLED) display comprising: a
substrate; an organic light emitting element positioned over the
substrate; and a first thin film transistor electrically connected
to the organic light emitting element and having a driving channel
region, wherein at least one groove is formed in the driving
channel region.
2. The OLED display of claim 1, further comprising a second thin
film transistor electrically connected to the first thin film
transistor and including a switching channel region.
3. The OLED display of claim 2, wherein the driving channel region
and the switching channel region are positioned on the same layer
over the substrate.
4. The OLED display of claim 3, wherein the first thin film
transistor further comprises a first gate electrode positioned in
the driving channel region and positioned in the groove, and
wherein the second thin film transistor further comprises a second
gate electrode positioned in the switching channel region.
5. The OLED display of claim 2, wherein the surface of the
switching channel region is substantially flat.
6. The OLED display of claim 1, wherein the groove has a curved
surface.
7. The OLED display of claim 1, wherein the organic light emitting
element comprises: a first electrode electrically connected to the
first thin film transistor; an organic emission layer positioned
over the first electrode; and a second electrode positioned over
the organic emission layer.
8. A method of manufacturing an organic light emitting diode (OLED)
display, comprising: forming a first thin film transistor including
a driving channel region on a substrate, wherein at least one
groove is formed in the driving channel region; and forming an
organic light emitting element electrically connected to the first
thin film transistor.
9. The method of claim 8, further comprising forming a second thin
film transistor electrically connected to the first thin film
transistor and including a switching channel region.
10. The method of claim 9, wherein the first thin film transistor
and the second thin film transistor are formed by the same
process.
11. The method of claim 10, wherein the forming of the first thin
film transistor and the forming of the second thin film transistor
include: forming a driving active layer and a switching active
layer over the substrate; forming a mask insulation layer including
an opening positioned corresponding to a position where a groove is
formed on the driving active layer and the switching active layer;
dry-etching the driving active layer through the opening to form a
preliminary groove at the driving active layer; dry-etching the
driving active layer through the opening to expand the preliminary
groove thereby forming the groove; and removing the mask insulation
layer.
12. The method of claim 11, wherein the preliminary groove is
formed as a plane, and wherein the groove has a curved surface.
Description
RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2012-0112470 filed in the Korean
Intellectual Property Office on Oct. 10, 2012, the entire contents
of which are incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The described technology generally relates to an organic
light emitting diode (OLED) display and a manufacturing method of
the display.
[0004] 2. Description of the Related Technology
[0005] Recently, an OLED display has received much attention as a
display device for displaying images.
[0006] The OLED display has a self-emission characteristic,
eliminating the necessity for a light source, unlike a liquid
crystal display (LCD) device, and thus can be fabricated to be
thinner and lighter. Also, the OLED display has high quality
characteristics such as low power consumption, high luminance, high
response speed, and the like.
SUMMARY
[0007] One inventive aspect is an organic light emitting diode
(OLED) display including a first thin film transistor connected to
an OLED, and a manufacturing method of the OLED display.
[0008] Another aspect is an organic light emitting diode (OLED)
display having a sufficient grayscale of light emitted from an
organic emission layer to improve display quality.
[0009] Another aspect is an organic light emitting diode (OLED)
display which includes: a substrate; an organic light emitting
element positioned on the substrate; and a first thin film
transistor connected to the organic light emitting element and
having a driving channel region including at least one groove.
[0010] A second thin film transistor connected to the first thin
film transistor and including a switching channel region may be
further included.
[0011] The driving channel region and the switching channel region
may be positioned with the same layer on the substrate.
[0012] The first thin film transistor may further include a first
gate electrode positioned on the driving channel region and
positioned in the groove, and the second thin film transistor
further may include a second gate electrode positioned on the
switching channel region.
[0013] The surface of the switching channel region may be flat.
[0014] The groove may be formed with a curved surface.
[0015] The organic light emitting element may include a first
electrode connected to the first thin film transistor, an organic
emission layer positioned on the first electrode, and a second
electrode positioned on the organic emission layer.
[0016] Another aspect is a manufacturing method of an organic light
emitting diode (OLED) display which includes forming a first thin
film transistor including a driving channel region having at least
one groove on a substrate, and forming an organic light emitting
element connected to the first thin film transistor.
[0017] The method may further include forming a second thin film
transistor connected to the first thin film transistor and
including a switching channel region.
[0018] The forming of the first thin film transistor and the
forming of the second thin film transistor may be performed with
the same process.
[0019] The forming of the first thin film transistor and the
forming of the second thin film transistor may include: forming a
driving active layer and a switching active layer on the substrate;
forming a mask insulation layer including an opening positioned
corresponding to a position where a groove will be formed on the
driving active layer and the switching active layer; dry-etching
the driving active layer through the opening to form a preliminary
groove at the driving active layer; dry-etching the driving active
layer through the opening to expand the preliminary groove thereby
forming the groove; and removing the mask insulation layer.
[0020] The preliminary groove may be formed as a plane, and the
groove may be formed with a curved surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a view of an organic light emitting diode (OLED)
display according to a first embodiment.
[0022] FIG. 2 is a layout view of a pixel part shown in FIG. 1.
[0023] FIG. 3 is a cross-sectional view taken along the line
III-III of FIG. 2.
[0024] FIG. 4 is a flowchart of a manufacturing method of an
organic light emitting diode (OLED) display according to a second
embodiment.
[0025] FIG. 5 to FIG. 9 are views to explain a manufacturing method
of an organic light emitting diode (OLED) display according to the
second embodiment.
DETAILED DESCRIPTION
[0026] Generally, an OLED display includes gate wires positioned on
a substrate and extending in one direction, data wires extending in
a direction crossing the gate wires, a plurality of thin film
transistors (TFTs) connected to the gate wires and the data wires,
and organic light emitting elements connected to the TFTs.
[0027] Recently, improvements in forming the channel region of a
TFT have led to improved driving capabilities. However, since a
driving range (DR) of the gate voltage applied to the gate
electrode of a TFT is very narrow, a grayscale of light emitted
from the OLED is narrow, thus leading to a loss in emission
quality.
[0028] Hereinafter, embodiments will be described more fully with
reference to the accompanying drawings. As those skilled in the art
would realize, the described embodiments may be modified in various
different ways, all without departing from the spirit or scope of
the present invention.
[0029] The drawings and description are to be regarded as
illustrative in nature and not restrictive. Like reference numerals
designate like elements throughout the specification.
[0030] Further, since sizes and thicknesses of constituent members
shown in the accompanying drawings are arbitrarily given for better
understanding and ease of description, the present invention is not
limited to the illustrated sizes and thicknesses.
[0031] In the drawings, the thickness of layers, films, panels,
regions, etc., may be exaggerated for clarity. In the drawings, for
better understanding and ease of description, the thicknesses of
some layers and areas are exaggerated. It will be understood that
when an element such as a layer, film, region, or substrate is
referred to as being "on" another element, it can be directly on
the other element or intervening elements may also be present.
[0032] In addition, unless explicitly described to the contrary,
the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements. Further,
throughout the specification, "on" implies being positioned above
or below a target element and does not imply being necessarily
positioned on the top on the basis of a gravity direction.
[0033] FIG. 1 is a view of an organic light emitting diode display
according to a first embodiment.
[0034] As shown in FIG. 1, an OLED display 1000 includes a
substrate SUB, a gate driver GD, gate wires GW, a data driver DD,
data wires DW, and a pixel PE. Here, the pixel PE is a minimum unit
displaying an image, and the OLED display 1000 displays the image
through a plurality of pixels PE.
[0035] The substrate SUB may be formed of a transparent light
transmissive substrate made of glass, quartz, ceramic, or plastic.
However, the substrate SUB can be formed as a metallic substrate
made of stainless steel. Further, when the substrate SUB is made of
plastic, the OLED display 1000 can be flexible, rollable, or
stretchable.
[0036] The gate driver GD sequentially supplies a scan signal to
the gate wires GW corresponding to a control signal supplied by a
control circuit (not shown), for example, a timing controller. The
pixel PE is selected by the scan signal to sequentially receive a
data signal.
[0037] The gate wires GW are positioned on the substrate SUB and
extend in the first direction. The gate wires GW include scan lines
S1-SCn, and the scan lines S1-SCn are connected to the gate driver
GD to receive scan signals from the gate driver GD.
[0038] In one embodiment, the gate wires GW include the scan lines
S1-SCn. The gate wires may further include an additional scan line,
an initial power source line, and a light emission control line. In
this case, the OLED display can be an active matrix (AM) type of
OLED display with a 6Tr-2Cap structure.
[0039] The data driver DD supplies a data signal to a data line DAm
from among the data wires DW corresponding to a control signal
supplied by the timing controller. The data signal supplied to the
data line DAm is supplied to the pixel PE selected by the scan
signal when the scan signal is supplied to the scan line SCn. The
pixel PE is charged with a voltage corresponding to the data signal
and emits light with corresponding luminance.
[0040] The data wires DW are positioned on the gate wires GW,
however they may be positioned between the gate wires GW and the
substrate SUB and may extend in the second direction crossing the
first direction. The data wires DW include the data lines DA1-DAm
and a driving power source line ELVDDL. The data lines DAm are
connected to the data driver DD and receive the data signal from
the data driver DD. The driving power source line ELVDDL is
connected to the first power source ELVDD from the outside and
receives driving power from the first power source ELVDD.
[0041] The pixel PE is positioned at a region where the gate wires
GW and the data wires DW are crossed, and includes an organic light
emitting element emitted with a luminance corresponding to the
driving current according to the data signal, a plurality of thin
film transistors to control a driving current flowing in the
organic light emitting element, and at least one capacitor. A
plurality of thin film transistors and at least one capacitor are
respectively connected to the gate wires GW and the data wires DW,
and the organic light emitting element is connected to a plurality
of thin film transistors and at least one capacitor. The organic
light emitting element is connected between the first power source
ELVDD and the second power source ELVSS.
[0042] FIG. 2 shows a layout view indicating a pixel part shown in
FIG. 1. FIG. 3 is a cross-sectional view taken along the line
III-III of FIG. 2.
[0043] As shown in FIG. 2 and FIG. 3, the pixel PE includes a pixel
circuit including the organic light emitting element connected
between the first power source ELVDD and the second power source
ELVSS, and two thin film transistors and one capacitor connected
between the organic light emitting element and the first power
source ELVDD to control a driving power source supplied to the
organic light emitting element.
[0044] The organic light emitting element includes the first
electrode E1, an organic emission layer OL positioned on the first
electrode E1, and the second electrode E2 positioned on the organic
emission layer OL. The first electrode E1 as an anode of the
organic light emitting element is connected to the driving power
line ELVDDL connected to the first power ELVDD through the pixel
circuit, and the second electrode E2 as a cathode of the organic
light emitting element is connected to the second power ELVSS. The
organic emission layer OL of the organic light emitting element is
supplied with the driving power through the first power ELVDD, and
the light is emitted with the luminance corresponding to the
driving current flowing to the organic light emitting element when
supplying a common power from the second power ELVSS. The organic
emission layer OL of the organic light emitting element may be
formed of a low molecular weight organic material or a high
molecular weight organic material such as PEDOT poly(3,4-ethylene
dioxythiophene). Further, the organic emission layer OL may be
formed as a multilayer including one or more of an emission layer,
a hole injection layer HIL, a hole transport layer HTL, an electron
transport layer ETL, and an electron injection layer EIL. In the
case where all the layers are included, the hole injection layer
HIL is disposed on a pixel electrode that is the anode, and the
hole transport layer HTL, the emission layer, the electron
transport layer ETL, and the electron injection layer EIL are
sequentially laminated thereon. The organic emission layer OL may
include a red organic emission layer emitting a red light, a green
organic emission layer emitting green light, and a blue organic
emission layer emitting blue light, and the red organic emission
layer, the green organic emission layer, and the blue organic
emission layer are respectively formed in a red pixel, a green
pixel, and a blue pixel thereby realizing a color image. Also, the
organic emission layer OL may realize the color image by depositing
all of the red organic emission layer, the green organic emission
layer, and the blue organic emission layer in the red pixel, the
green pixel, and the blue pixel and forming a red color filter, a
green color filter, and a blue color filter for each pixel. As
another example, a white organic emission layer emitting white
light is formed in all of the red pixel, the green pixel, and the
blue pixel, and the red color filter, the green color filter, and
the blue color filter are respectively formed for each pixel
thereby realizing the color image. When realizing the color image
by using the white organic emission layer and the color filter, it
is not necessary to use a deposition mask to respectively form the
red organic emission layer, the green organic emission layer, and
the blue organic emission layer such that an image resolution is
improved.
[0045] The pixel circuit includes the first thin film transistor
T1, the second thin film transistor T2, and a capacitor C.
[0046] The first thin film transistor T1 is connected between the
driving power source line ELVDDL and the first electrode E1 of the
organic light emitting element and supplies the driving power
source corresponding to the data signal from the first power source
ELVDD to the organic light emitting element during a light emitting
period of the pixel PE. That is, the first thin film transistor T1
functions as a driving transistor of the pixel PE.
[0047] The first thin film transistor T1 includes the first source
electrode S1, the first drain electrode D1, a driving channel
region CH1, and the first gate electrode G1.
[0048] The first source electrode S1 is connected to the driving
power source line ELVDDL, and the first drain electrode D1 is
separated from the first source electrode S1 via a driving channel
region CH1 and is connected to the organic light emitting element.
The first source electrode S1 and the first drain electrode D1 are
formed with a different layer from the driving channel region CH1,
however the first source electrode S1 and the first drain electrode
D1 may be formed with the same layer as the driving channel region
CH1. In this case, an impurity may be injected to the first source
electrode S1 and the first drain electrode D1.
[0049] The driving channel region CH1 is connected to the first
capacitor electrode CE1 of the capacitor C, and is positioned
between the first source electrode S1 and the first drain electrode
D1. The driving channel region CH1 includes a plurality of grooves
GV that are depressed from a surface thereof. The grooves GV are
formed with a curved surface thereby substantially forming a
partial circle. The groove GV may be formed of a straight line, a
curved line, or an island shape on the surface of the driving
channel region, and one or a plurality of driving channel regions
CH1 may be formed.
[0050] The groove GV is formed in the driving channel region CH1
such that the entire channel length of the driving channel region
CH1 is increased. The driving channel region CH1 may be formed of
polysilicon or an oxide semiconductor. The oxide semiconductor may
be made of an oxide basically including zinc (Zn), gallium (Ga),
tin (Sn), or indium (In), or a composite oxide thereof such as zinc
oxide (ZnO), indium-gallium-zinc oxide (InGaZnO4), indium-zinc
oxide (Zn--In--O), or zinc-tin oxide (Zn--Sn--O). When the driving
channel region CH1 is formed of the oxide semiconductor, a
protection layer protecting the oxide semiconductor that is weak
against external environment factors such as a high temperature may
be added on the driving channel region CH1. A source region and a
drain region are positioned at both ends of the driving channel
region CH1, and the source region and the drain region may be
respectively injected with the impurity. The driving channel region
CH1, the source region, and the drain region form a driving active
layer A1.
[0051] The first gate electrode G1 is positioned on the driving
channel region CH1 and is connected to the second drain electrode
D2 of the second thin film transistor T2. The first gate electrode
G1 is positioned in the groove GV.
[0052] The second thin film transistor T2 connects the data line
Dam and the first thin film transistor T1. The second thin film
transistor T2 transmits the data signal supplied from the data line
Dam in the pixel PE when the scan signal is supplied from the scan
line SCn. That is, the second thin film transistor T2 functions as
the switching transistor of the pixel PE.
[0053] The second thin film transistor T2 includes the second
source electrode S2, the second drain electrode D2, a switching
channel region CH2, and the second gate electrode G2.
[0054] The second source electrode S2 is connected to the data line
Dam and the second drain electrode D2 is connected to the first
gate electrode G1 of the first thin film transistor T1. The second
source electrode S2 and the second drain electrode D2 are formed
with a different layer from the switching channel region CH2,
however the second source electrode S2 and the second drain
electrode D2 may be formed with the same layer as the switching
channel region CH2. In this case, the second source electrode S2
and the second drain electrode D2 may be injected with the
impurity.
[0055] The switching channel region CH2 is positioned with the
island shape between the second source electrode S2 and the second
drain electrode D2. The surface of the switching channel region CH2
is flat, different from the driving channel region CH1. The
switching channel region CH2 has the flat surface such as the
switching channel region CH2 has a shorter channel length than that
of the driving channel region CH1. The switching channel region CH2
is positioned with the same layer as the driving channel region CH1
on the substrate SUB and is formed with the same material. The
switching channel region CH2 may be made of polysilicon or the
oxide semiconductor. The source region and the drain region are
positioned at both ends of the switching channel region CH2, and
the source region and the drain region may be injected with the
impurity. The switching channel region CH2, the source region, and
the drain region form a switching active layer A2.
[0056] The second gate electrode G2 is positioned on the switching
channel region CH2 and is connected to the scan line SCn.
[0057] The capacitor C includes the first capacitor electrode CE1
and the second capacitor electrode CE2 facing each other via an
insulation layer interposed therebetween. The first capacitor
electrode CE1 is connected to the driving power source line ELVDDL,
and the second capacitor electrode CE2 is connected to the second
gate electrode G2 of the second thin film transistor T2 through the
first gate electrode G1.
[0058] If the switching thin film transistor T2 is instantly turned
on, the power is supplied from the driving power source line ELVDDL
to the first capacitor electrode CE1 of the capacitor C and
simultaneously the power is supplied to second capacitor electrode
CE2 from the data line Dam through the switching thin film
transistor T2 such that the capacitor C is charged. At this time,
the charge amount is proportional to the voltage applied from the
data line DAm. In the state that the switching thin film transistor
T2 is turned off, the gate potential of the driving thin film
transistor T1 is increased according to the potential charged to
the capacitor C. Also, the driving thin film transistor T1 is
turned on if the gate potential is over the threshold voltage.
Thus, the voltage applied to the driving power source line ELVDDL
is applied to the organic light emitting element through the
driving thin film transistor T1 such that the organic light
emitting element emits light.
[0059] The above-noted configuration of the pixel PE is not
restricted to the description, and is variable in many ways within
a range that is easily modifiable by a person skilled in the
art.
[0060] As described above, the second thin film transistor T2
includes the switching channel region CH2 having the flat surface
of which the channel length is decreased compared with the driving
channel region CH1 of the first thin film transistor T1 such that
the load of the driving current flowing in the pixel PE is
minimized. Also, the first thin film transistor T1 controlling the
driving current supplied to the organic light emitting element
(OLED) substantially includes the driving channel region CH1 having
at least one groove GV such that the entire channel length of the
driving channel region CH1 is increased, and accordingly, when the
light emitted from the organic emission layer (OL) of the organic
light emitting element according to the driving current flowing in
the organic light emitting element is displayed as a black color
and a white color, the driving range (DR) of the gate voltage
applied to the first gate electrode G1 of the first thin film
transistor T1 is wide.
[0061] In one embodiment, the OLED display 1000 minimizes the load
of the driving current passing through the second thin film
transistor T2, and simultaneously the driving range (DR) of the
first thin film transistor T1 is increased, and accordingly, light
emitted from the OLED can be controlled to have sufficient grays by
changing the magnitude of the gate voltage applied to the first
gate electrode G1 of the first thin film transistor T1.
[0062] Recently, the number of pixels per inch (ppi) of the OLED
display 1000 has increased such that the high driving range (DR) is
required for the light emitted from the organic light emitting
element to have sufficient grays for realizing the OLED display
1000 of the high resolution. In one embodiment, the OLED display
1000 is controlled to have sufficient grays, thereby providing the
OLED display 1000 having high resolution and simultaneously
improved display quality.
[0063] Also, the semiconductor characteristic of the driving
channel region CH1 of the first thin film transistor T1 is poor due
to the groove GV, and since the first thin film transistor T1
requires the high threshold voltage compared with the second thin
film transistor T2, undesired light emitting of the organic light
emitting element is suppressed in the low grayscale region such
that spots generated in the image displayed by the organic light
emitting element are minimized.
[0064] Also, the switching channel region CH2 of the second thin
film transistor T2 that is the switching thin film transistor among
a plurality of thin film transistors has a short channel length
such that the semiconductor characteristic is good compared with
the driving channel region CH1. Accordingly, each charge mobility
of the second thin film transistor T2 is increased, and
simultaneously the threshold voltage is decreased, and thereby the
second thin film transistor T2 may perform the turn-on and the
turn-off with a fast speed. Therefore, the load of the current
flowing in the entire OLED display 1000 is minimized such that the
display quality of the OLED display 1000 is improved. That is, the
OLED display 1000 having the high resolution and simultaneously the
improved display quality is provided.
[0065] Next, a manufacturing method of an OLED display according to
a second embodiment will be described with reference to FIG. 4 to
FIG. 9. The OLED display 1000 according to the first embodiment may
be manufactured by the method of the second embodiment.
[0066] FIG. 4 is a flowchart of a manufacturing method of an OLED
display according to the second embodiment. FIG. 5 to FIG. 9 are
views to explain a manufacturing method of an OLED display
according to the second embodiment.
[0067] Firstly, as shown in FIG. 4, the first thin film transistor
and the second thin film transistor formed with the same process
(S100 and S200).
[0068] In detail, firstly, as shown in FIG. 5, a driving active
layer A1 and a switching active layer A2 are formed on a substrate
SUB. The driving active layer A1 and the switching active layer A2
are made of polysilicon or the oxide semiconductor.
[0069] Next, a mask insulation layer MI having openings OA
positioned corresponding to a position where the above-described
groove will be formed is formed on the driving active layer A1 and
the switching active layer A2. The mask insulation layer MI may
include an inorganic material such as silicon nitride or silicon
oxide.
[0070] Next, as shown in FIG. 6, by using an etching means such as
plasma or an ion beam, the driving active layer A1 is dry-etched
through the opening OA to form a preliminary groove PSV at the
driving channel region CH1 of the driving active layer A1. The
preliminary groove PSV is formed in a plane according to a
characteristic of the dry etching. The preliminary groove PSV may
have a polygonal shape such as a quadrangle or a triangle.
[0071] Next, as shown in FIG. 7, by using an etching means such as
an etchant, the driving active layer Al is dry-etched through the
opening OA to expand the preliminary groove PSV of the driving
channel region CH1 of the driving active layer Al thereby forming a
groove GV. The groove GV is formed with a curved surface according
to the characteristic of the dry etching. The groove GV may have a
circular shape.
[0072] Next, as shown in FIG. 8, the mask insulation layer MI is
removed.
[0073] Next, as shown in FIG. 9, the first gate electrode G1, the
second gate electrode G2, the first source electrode SI, the first
drain electrode D1, the second source electrode S2, and the second
drain electrode D2 are formed on the driving active layer A1 and
the switching active layer A2 to form the first thin film
transistor T1 and the second thin film transistor T2. At this time,
the above-described capacitor may be simultaneously formed.
[0074] Next, an organic light emitting element (OLED) is formed
(S300).
[0075] In detail, an insulation layer such as a planarization layer
is formed on the first thin film transistor T1, and the first
electrode E1 connected to the first thin film transistor T1, an
organic emission layer (OL), and the second electrode E2 are
sequentially formed thereby forming the organic light emitting
element connected to the first thin film transistor T1.
[0076] As described above, the second thin film transistor T2
includes the switching channel region CH2 having the flat surface
with the decreased channel length compared with the driving channel
region CH1 of the first thin film transistor T1 such that the load
of the driving current flowing in the pixel PE is minimized. Also,
the first thin film transistor T1 substantially controlling the
driving current supplied to the organic light emitting element
includes the driving channel region CH1 having at least one groove
GV to increase the entire channel length of the driving channel
region CH1, and when the light emitted from the organic emission
layer (OL) of the organic light emitting element according to the
driving current flowing in the organic light emitting element is
displayed from a black color to a white color, the driving range
(DR) of the gate voltage applied to the first gate electrode G1 of
the first thin film transistor T1 is wide.
[0077] According to at least one of the disclosed embodiments, the
grayscales of the light emitted from the organic emission layer are
sufficient such that a display quality of an OLED is enhanced.
[0078] While the above embodiments have been described with
reference to the accompanying drawings, it is to be understood that
the invention is not limited to the disclosed embodiments, but, on
the contrary, is intended to cover various modifications and
equivalent arrangements included within the spirit and scope of the
appended claims.
* * * * *